postgres.git / summary / log / commit / refs
commit 0f359c7de9f5f8fceedfebfae0b0cbbf01d1f5bf
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu Feb 18 20:40:36 2016 +0000
Fix multiple bugs in contrib/pgstattuple's pgstatindex() function.
Dead or half-dead index leaf pages were incorrectly reported as live, as a
consequence of a code rearrangement I made (during a moment of severe brain
fade, evidently) in commit d287818eb514d431.
The index metapage was not counted in index_size, causing that result to
not agree with the actual index size on-disk.
Index root pages were not counted in internal_pages, which is inconsistent
compared to the case of a root that's also a leaf (one-page index), where
the root would be counted in leaf_pages. Aside from that inconsistency,
this could lead to additional transient discrepancies between the reported
page counts and index_size, since it's possible for pgstatindex's scan to
see zero or multiple pages marked as BTP_ROOT, if the root moves due to
a split during the scan. With these fixes, index_size will always be
exactly one page more than the sum of the displayed page counts.
Also, the index_size result was incorrectly documented as being measured in
pages; it's always been measured in bytes. (While fixing that, I couldn't
resist doing some small additional wordsmithing on the pgstattuple docs.)
Including the metapage causes the reported index_size to not be zero for
an empty index. To preserve the desired property that the pgstattuple
regression test results are platform-independent (ie, BLCKSZ configuration
independent), scale the index_size result in the regression tests.
The documentation issue was reported by Otsuka Kenji, and the inconsistent
root page counting by Peter Geoghegan; the other problems noted by me.
Back-patch to all supported branches, because this has been broken for
a long time.
contrib/pgstattuple/pgstatindex.c | 16 ++++++----------
doc/src/sgml/pgstattuple.sgml | 15 +++++++++++----
2 files changed, 17 insertions(+), 14 deletions(-)
diff --git a/contrib/pgstattuple/pgstatindex.c b/contrib/pgstattuple/pgstatindex.c
index ceabd862a86..0aa517a870a 100644
--- a/contrib/pgstattuple/pgstatindex.c
+++ b/contrib/pgstattuple/pgstatindex.c
@@ -66,7 +66,6 @@ typedef struct BTIndexStat
uint32 level;
BlockNumber root_blkno;
- uint64 root_pages;
uint64 internal_pages;
uint64 leaf_pages;
uint64 empty_pages;
@@ -133,7 +132,6 @@ pgstatindex(PG_FUNCTION_ARGS)
}
/* -- init counters -- */
- indexStat.root_pages = 0;
indexStat.internal_pages = 0;
indexStat.leaf_pages = 0;
indexStat.empty_pages = 0;
@@ -166,7 +164,11 @@ pgstatindex(PG_FUNCTION_ARGS)
/* Determine page type, and update totals */
- if (P_ISLEAF(opaque))
+ if (P_ISDELETED(opaque))
+ indexStat.deleted_pages++;
+ else if (P_IGNORE(opaque))
+ indexStat.empty_pages++; /* this is the "half dead" state */
+ else if (P_ISLEAF(opaque))
{
int max_avail;
@@ -183,12 +185,6 @@ pgstatindex(PG_FUNCTION_ARGS)
if (opaque->btpo_next != P_NONE && opaque->btpo_next < blkno)
indexStat.fragments++;
}
- else if (P_ISDELETED(opaque))
- indexStat.deleted_pages++;
- else if (P_IGNORE(opaque))
- indexStat.empty_pages++;
- else if (P_ISROOT(opaque))
- indexStat.root_pages++;
else
indexStat.internal_pages++;
@@ -220,7 +216,7 @@ pgstatindex(PG_FUNCTION_ARGS)
snprintf(values[j++], 32, "%d", indexStat.level);
values[j] = palloc(32);
snprintf(values[j++], 32, INT64_FORMAT,
- (indexStat.root_pages +
+ (1 + /* include the metapage in index_size */
indexStat.leaf_pages +
indexStat.internal_pages +
indexStat.deleted_pages +
diff --git a/doc/src/sgml/pgstattuple.sgml b/doc/src/sgml/pgstattuple.sgml
index a55b35cb3f1..7f1ae8d3048 100644
--- a/doc/src/sgml/pgstattuple.sgml
+++ b/doc/src/sgml/pgstattuple.sgml
@@ -146,13 +146,13 @@ test=> SELECT * FROM pgstatindex('pg_cast_oid_index');
-[ RECORD 1 ]------+------
version | 2
tree_level | 0
-index_size | 8192
+index_size | 16384
root_block_no | 1
internal_pages | 0
leaf_pages | 1
empty_pages | 0
deleted_pages | 0
-avg_leaf_density | 50.27
+avg_leaf_density | 54.27
leaf_fragmentation | 0
</programlisting>
</para>
@@ -186,13 +186,13 @@ leaf_fragmentation | 0
<row>
<entry><structfield>index_size</structfield></entry>
<entry><type>bigint</type></entry>
- <entry>Total number of pages in index</entry>
+ <entry>Total index size in bytes</entry>
</row>
<row>
<entry><structfield>root_block_no</structfield></entry>
<entry><type>bigint</type></entry>
- <entry>Location of root block</entry>
+ <entry>Location of root page (zero if none)</entry>
</row>
<row>
@@ -236,6 +236,13 @@ leaf_fragmentation | 0
</informaltable>
</para>
+ <para>
+ The reported <literal>index_size</> will normally correspond to one more
+ page than is accounted for by <literal>internal_pages + leaf_pages +
+ empty_pages + deleted_pages</literal>, because it also includes the
+ index's metapage.
+ </para>
+
<para>
As with <function>pgstattuple</>, the results are accumulated
page-by-page, and should not be expected to represent an
[parent: 875973f5d756]